Correct Option (C)
Pairs 3 and 4 are correctly matched.
The Volga River is the longest river in Europe and flows into the Caspian Sea, which is an endorheic basin.
The Zambezi River is a major river in Southern Africa. It flows eastward across the continent and empties into the Indian Ocean. It is also known for forming the Victoria Falls.
Incorrect Options:
Pair 1 is incorrectly matched. The Mekong River, a significant trans-boundary river in Southeast Asia, flows into the South China Sea, primarily through its delta in Vietnam, not the Andaman Sea.
Pair 2 is incorrectly matched. The River Thames flows through southern England and discharges into the North Sea, not the Irish Sea.